1. Field of the Invention
Embodiments of the present invention relate to an adaptive variable block transform system, medium, and method, including at least a system, medium, and method for adaptive variable block transforming and a system, medium, and method for video encoding/coding for variable block coding, and more particularly, an adaptive variable block transform system, medium, and method for variable block transform, in which high compression efficiency can be obtained by performing a variable block transform based on various video characteristics, including at least a color format and/or the characteristics of components of a respective color system. The variable block transform may be performed on not only luminance components or one color component, for example, but also remaining chrominance or other color components, for example.
2. Description of the Related Art
In conventional video compression, to encode a temporal sequence of image frames, each of the image frames is divided into blocks of a predetermined size, for example, and redundant information of each of the blocks is removed through compression, e.g., using transform coding. In recently standardized ISO/IEC MPEG and H.264/AVC (ITU-T Recommendation H.264 and ISO/IEC 14496-10 (MPEG-4 part 10) Advanced Video Coding) of Joint Video Team of ITU-T VCEG, which will herein be referred to as the current H.264/AVC, 4×4 integer transform is basically used, with discrete cosine (DC) transform being additionally performed on DC components of each of 4×4 blocks of a 16×16 macroblock. At the same time, a 8×8 transform is performed on only luminance components. In this case, luminance components of every block or macroblock of an image frame will be transform-coded using 4×4 or 8×8 transform.
However, as predefined in the current H.264/AVC, as noted, 4×4 or 8×8 transform is performed only on luminance components, with only a 4×4 transform being performed on chrominance components. This is because the current H.264/AVC was initially developed only for the YCbCr 4:2:0 format, in which chrominance components of an input image are sub-sampled at ¼ of the sub-sampling of the luminance components of the input image. However, with the increasing demands for high-quality images, there has been a suggestion to expand the current H.264/AVC to support not only YCbCr 4:2:0 but also YCbCr 4:2:2, YCbCr 4:4:4, as well as RGB or alternate XYZ formats, i.e., image information represented by multiple components other than the RGB and YCbCr formats. However, during such an expansion of the current H.264/AVC, different block transform coding is not correctly applied for these different formats. Therefore, to achieve low quality loss and high compression rates during compression of a high-quality image, there is a need for a method for applying block transform suitable for both luminance and chrominance components. In addition, there is a need for a color component adaptive transform system, medium, or method that makes the most of a conventional technique, e.g., the current H.264/AVC standard, with minimum changes.